Summer surveys (Julyb??August) of juvenile salmon ecology along the continental shelf of the Gulf of Alaska are conducted annually by scientists from the Ocean Carrying Capacity program of the National Marine Fisheries Serviceb??s Auke Bay Laboratory. These surveys are an effort to link changes in salmon production to biological and physical factors in the ocean environment. An improved understanding of salmon distribution is one objective of this research. We identified the origin of juvenile chum salmon collected in transects from around the Gulf of Alaska in 2000 and 2001, using the presence of thermal marks in hatchery fish and the divergence of genetic characteristics among regional groups of populations.

Allozymes from 46 loci were analyzed from chum salmon (Oncorhynchus keta) collected at 61 locations in southeast Alaska and northern British Columbia. Of the 42 variable loci, 21 had a common allele frequency <0.95. We observed significant heterogeneity within and among six regional groups: central southeast Alaska, Prince of Wales Island area, southern southeast Alaska b?? northern British Columbia, north-central British Columbia, and two groups in the Queen Charlotte Islands. Genetic variation among regions was significantly greater than within regions. The three island groups were distinct from each other and from the mainland populations. Allele frequencies were stable over time in 14 of 15 locations sampled for more than 1 yr. The geographic basis for heterogeneity among regions is confounded in part by spawning-time differences. The Prince of Wales and Queen Charlotte populations spawn in the fall; the mainland populations spawn mainly in the summer, although some overlap exists. Overall, most genetic diversity (97%) occurred within sampling locations; the remaining diversity was distributed almost equally within and among regions. Our genetic data may provide fishery managers a means to estimate stock composition in the mixed-stock fisheries near this boundary between the United States and Canada.

Genetic stock identification techniques were used to identify the origin and provide stock-specific migration and distribution patterns of juvenile chum (Oncorhynchus keta) salmon caught during annual fall surveys (2002) along the eastern Bering Sea (Fig. 1). Preliminary results indicate that: 1) Yukon River Fall chum salmon are widely distributed from offshore of the Yukon River, eastward to 62B0N, 172B0W, and as far south as Nunivak Island (60B0N), suggesting a southwesterly migration pathway along the Bering Sea shelf; 2) juvenile chum salmon from the Kuskokwim River are narrowly distributed south of Nunivak Island from the mouth of the Kuskokwim River, south to 58B0N, and as far west as 168B0W, suggesting a westerly migration pathway along the Bering Sea shelf; and 3) northern Russia juvenile chum salmon stocks (mainly stocks from rivers draining into the Gulf of Anadyr) are distributed as far east as 62B0N, 171B0W (Fig. 2). These results are unique in that they represent the first attempt to identify early marine distribution and migration of juvenile chum salmon stocks on the eastern Bering Sea shelf.

A genetic analysis of samples from the chum salmon (Oncorhynchus keta) bycatch of the 2005 Bering Sea walleye pollock (Theragra chalcogramma) trawl fishery was undertaken to determine the overall stock composition of the sample set. Samples were genotyped for eleven microsatellite markers and results were estimated using the current chum salmon microsatellite baseline. In 2005, genetic samples were collected opportunistically as part of a special project and supplemented with archived scales from the Observer Program. Sample biases have the potential to affect stock composition analysis results; consequently, stock composition estimates apply to the sample set and may not represent the entire chum salmon bycatch. Based on the analysis of 1,084 chum salmon bycatch samples collected throughout the 2005 Bering Sea trawl fishery, East Asian (29%), North Asian (29%), Pacific Northwest (19%) and Western Alaska (16%) stocks dominated the sample set with smaller contributions from Southwest Alaska (<2%) and the Upper/Middle Yukon River (5%) stocks. The estimates for the 2005 chum salmon bycatch sample set were similar to the 1994-1995 chum salmon bycatch estimates, suggesting consistency of the regional stock contributions across years. Analysis of temporal groupings within the groundfish B season revealed changes in stock composition during the course of the season. Whether the decreasing proportional contributions of Western Alaska and Upper/Middle Yukon stocks and increasing proportional contributions from Asia over time are due to temporal or spatial differences in the sample set are unknown.

A genetic analysis of samples from the chum salmon (Oncorhynchus keta) bycatch of the 2010 Bering Sea groundfish trawl fishery was undertaken to determine the overall stock composition of the sample set. Samples were genotyped for 11 microsatellite markers and results were estimated using the current chum salmon microsatellite baseline. In 2010, genetic samples were collected as part of the species composition analysis of the Alaska Fisheries Science Centers North Pacific Observer Program. This sampling change for 2010 was an interim measure implemented until the systematic sampling protocols are finalized. Consequently, stock composition estimates apply to the sample set and may not represent the entire chum salmon bycatch. Based on the analysis of 1,048 chum salmon bycatch samples collected throughout the 2010 Bering Sea trawl fishery, East Asian (38%), North Asian (26%), Western Alaska (14%), and Eastern Gulf of Alaska/Pacific Northwest (13%) stocks dominated the sample set, with smaller contributions from Upper/Middle Yukon River (7%) stocks. The estimates for the 2010 chum salmon bycatch sample set were similar to the 20052009 chum salmon bycatch estimates, suggesting consistency of the regional stock contributions across years. Analysis of temporal groupings within the groundfish B season revealed changes in stock composition during the course of the season with decreasing contribution of Western Alaska and Eastern Gulf of Alaska/Pacific Northwest stocks and increasing contribution of North Asian stocks over time, but leaves unanswered whether these changes are due to temporal or spatial differences in the sample set.

A genetic analysis of samples from the chum salmon (Oncorhynchus keta) bycatch from the 2012 Bering Sea walleye pollock (Gadus chalcogrammus) trawl fishery was undertaken to determine the overall stock composition of the sample set. A genetic analysis of chum salmon collected during a test of a salmon excluder device was also conducted. Samples were genotyped for 11 microsatellite markers and results were estimated using the current chum salmon microsatellite baseline. In 2012, genetic samples were collected systematically as part of a special project that commenced in 2011 to reduce sample biases that exist in collections from previous years and have the potential to affect stock composition analysis results. One genetic sample was collected for every 31.5 chum salmon caught in the 98% of the midwater trawl fishery that was sampled. Evaluation of sampling based on time, location, and vessel indicated that the genetic samples were representative of the total bycatch. Based on the analysis of 673 chum salmon bycatch samples collected throughout the 2012 Bering Sea trawl fishery, the North Asian stocks dominated the sample set (39%), with moderate contributions from East Asian (20%), Eastern Gulf of Alaska (GOA)/Pacific Northwest (PNW) (18%), and Western Alaska (14%) stocks, and smaller contributions from Upper/Middle Yukon River (7%) and Southwest Alaska (2%) stocks. The estimates for the 2012 chum salmon bycatch sample set differed from the mean of the 20052011 estimates for the two Asian regions, but not for the North American regions. The pattern of changes of regional stock contributions over three time periods in 2012 differed from previous years for some regions. There were some spatial differences in stock distribution; e.g., the East Asian stock contribution was higher in the central Bering Sea than in the southeastern Bering Sea. As with the bycatch samples, the salmon excluder device test samples included fish from all geographic regions despite being collected at small spatial and temporal scales.

A genetic analysis of samples from the chum salmon (Oncorhynchus keta) bycatch from the 2011 Bering Sea walleye pollock (Theragra chalcogramma) trawl fishery was undertaken to determine the overall stock composition of the sample set. Samples were genotyped for 11 microsatellite markers and results were estimated using the current chum salmon microsatellite baseline. In 2011, genetic samples were collected systematically as part of a special project to reduce sample biases that exist in collections from previous years that have the potential to affect stock composition analysis results. One genetic sample was collected for every 31.1 chum salmon caught in 97% of the midwater trawl fishery that was sampled. Evaluation of sampling based on time, location, and vessel indicated that the genetic samples were representative of the total bycatch. Based on the analysis of 1,472 chum salmon bycatch samples collected throughout the 2011 Bering Sea trawl fishery, the Eastern Gulf of Alaska (GOA)/Pacific Northwest (PNW) stocks dominated the sample set (38%), with moderate contributions from East Asian (17%), North Asian (18%), and Western Alaska (16%) stocks, and smaller contributions from Upper/Middle Yukon River (9%) stocks. The estimates for the 2011 chum salmon bycatch sample set differed from the 20052010 estimates, indicating a change in the consistency of the regional stock contributions across the previous 6 years, possibly due to the larger proportion of bycatch caught later in the season and in the more southeastern NMFS reporting areas in 2011. There were significant spatial differences in stock distribution, with the Asian stocks dominating the central Bering Sea area and the Eastern GOA/PNW stocks dominating the southeastern Bering Sea. Analysis of temporal groupings revealed changes in stock composition during the course of the season with decreasing contribution of East Asia and Upper/Middle Yukon stocks and increasing contribution of Eastern GOA/PNW stocks over time.

A genetic analysis of samples from the chum salmon (Oncorhynchus keta) bycatch of the 2008 Bering Sea walleye pollock (Theragra chalcogramma) trawl fishery was undertaken to determine the overall stock composition of the sample set. Samples were genotyped for eleven microsatellite markers and results were estimated using the current chum salmon microsatellite baseline. In 2008, genetic samples were collected opportunistically as part of a special project, but sample biases have the potential to affect stock composition analysis results. Consequently, stock composition estimates apply to the sample set and may not represent the entire chum salmon bycatch. Based on the analysis of 629 chum salmon bycatch samples collected throughout the 2008 Bering Sea trawl fishery, North Asian (27%), East Asian (35%), and Eastern Gulf of Alaska/Pacific Northwest (24%) stocks dominated the sample set, with smaller contributions from western Alaska (7%) and Upper/Middle Yukon River (6%) stocks. The estimates for the 2008 chum salmon bycatch sample set were similar to the 2005, 2006, 2007, and 2009 chum salmon bycatch estimates, suggesting consistency of the regional stock contributions across years. Analysis of temporal groupings within the groundfish B season revealed changes in stock composition during the course of the season with decreasing contribution of Eastern Gulf of Alaska/Pacific Northwest stocks over time, but leaves unanswered whether these changes are due to temporal or spatial differences in the sample set.

A genetic analysis of samples from the chum salmon (Oncorhynchus keta) bycatch of the 2007 Bering Sea walleye pollock (Theragra chalcogramma) trawl fishery was undertaken to determine the overall stock composition of the sample set. Samples were genotyped for eleven microsatellite markers and results were estimated using the current chum salmon microsatellite baseline. In 2007, genetic samples were collected opportunistically as part of a special project, but sample biases have the potential to affect stock composition analysis results. Consequently, stock composition estimates apply to the sample set and may not represent the entire chum salmon bycatch. Based on the analysis of 1,279 chum salmon bycatch samples collected throughout the 2007 Bering Sea trawl fishery, North Asian (35%), East Asian (34%), and Eastern Gulf of Alaska/Pacific Northwest (16%) stocks dominated the sample set, with smaller contributions from Western Alaska (10%) and Upper/Middle Yukon River (5%) stocks. The estimates for the 2007 chum salmon bycatch sample set were similar to the 2005, 2006, and 2009 chum salmon bycatch estimates, suggesting consistency of the regional stock contributions across years. Analysis of temporal groupings within the groundfish B season revealed changes in stock composition during the course of the season with decreasing contribution of Upper/Middle Yukon stocks over time, but leaves unanswered whether these changes are due to temporal or spatial differences in the sample set.

A genetic analysis of samples from the chum salmon (Oncorhynchus keta) bycatch of the 2009 Bering Sea walleye pollock (Theragra chalcogramma) trawl fishery was undertaken to determine the overall stock composition of the sample set. Samples were genotyped for eleven microsatellite markers and results were estimated using the current chum salmon microsatellite baseline. In 2009, genetic samples were collected opportunistically as part of a special project, but sample biases have the potential to affect stock composition analysis results. Consequently, stock composition estimates apply to the sample set and may not represent the entire chum salmon bycatch. Based on the analysis of 1,437 chum salmon bycatch samples collected throughout the 2009 Bering Sea trawl fishery, North Asian (30%), East Asian (34%), and Eastern Gulf of Alaska/Pacific Northwest (18%) stocks dominated the sample set, with smaller contributions from Western Alaska (13%), Upper/Middle Yukon River (2%), and Southwest Alaska (4%) stocks. The estimates for the 2009 chum salmon bycatch sample set were similar to the 2005 chum salmon bycatch estimates.